Treatment of photographic films



Sept. 3, 1940. F. J. J. STOCK TREATMENT OF PHOTOGRAPHIC FILMS Filed Jan. 25, 1.938

IOL n e m 1T a n .Prior to y Coating l 7xeriormagela15er .5 Image lager innermost im age lager idhesiye prepa mfofy v lager Cellu Zo ncl earner Affar Treamen A t Orneys r Patented Sept. 3, 1940 Friedrich J ohann Jacob Stock, Berlin, Germany Application January 25, 1938, Serial No.l 186,799

l In Germany September 23, 1936 2 Claims.

This invention relates to a method of treating photographic colour films of the kind comprising a carrier film, a plurality of superposed image layers and separating layers between the adjacent image layers, and to a colour film treated in accordance with this process.

It is an object of this invention to improve the luminosity and transparency of fresh or used colour lms of this kind by changing substantially the mechanical state of the superposed image and separating layers and without acting upon the dye-stuff proper which is incorporated in the image layers.

Another object of my invention is to remove the separating layers which after the nlm has beendyed do not have any useful function but impair the brilliance of the colours and increase the distance between the superposed layers which o for optical reasons should be as small as possible.

Still another object of the invention is to remove the detrimental effect of the irregular surfaces of the cavities which are formed in the image layers as the silver grains are removed in the photographic treatment, and tend to refract 5 the light transmitted through the film,

According to this invention, the film is treated with a liquid, mixture of liquids or solution, which is capable of swelling the image layers to adegree nearly causing said image layers to adopt a sol condition. This state is hereinafter called maximum swelling for the purpose of this speciication. The liquid moreover comprises substances adapted to dissolve or to dialyze through, the separating layers of the nlm. Thus the liquid penetrates through all separating layers downto the innermost image layer, whereby the irregular bounding surfaces of the cavities in the image layers are superficially converted to a sol and smoothened. Moreover, where solvents for the separating layers are used, the separating layers are dissolved in the treatment with the liquid and absorbed by the adjacent swollen image layers. 'I'he cavities in' the image layers are at least partly lilled up by the solid substances contained in 15 the dissolved adjacent separating layers and/or dispersed or dissolved lin the liquid which has been used forlthe treatment.

l A schematical cross section ofl a colour film of r the kind with which this invention is concerned, D before and after the treatment, has been illustrated by way of example and schematically in the accompanying drawing.

Referring now to the drawing, prior to the treatment the carrier layer I of the film, consist- 55 ing of celluloid, carries a preparatory layer 2 of any suitable material adapted to facilitate the adhesion of the following layers, viz:

An innermost image layer 3, preferably representing the blue-green colour layer, a separating B0 layer 4, a second image layer 5, preferably repre- (ci. as z) senting the magenta colour layer, a second separating layer 6, and a third or exterior image layer 1, preferably representing the yellow colour layer It will .be understood that the separating layers 4 and 6 are merely provided, in the manner known `per s e, in order to prevent the substance used in .the dyeing process for causing the layer to adopt a red colour, from affecting the layer 3, or in order to prevent the substance used in the dyeing process to dye the yellow layer 'l from affecting the layers 5 and 3, respectively. Therefore, after the dyeing process, these separating layers or blocking layers not only do not serve any useful purpose but are positively harmful to the luminosity of the colours, the transparency of the film and sharpness of the contours. Some of the hollows or cavities produced by the removal of the silver grains are indicated at 8 andit will be seen that the cavities vhave veryl irregular contours causing undesirable refraction of the light transmitted through the film. Of course, the cavities 8 have been shown exaggerated both in scale and shape.

Now, after the treatment, the celluloid layer I and the layer 2 have remained substantially unchanged except that the separating line between the layers 2 and 3 is less sharp and distinct, due to the swelling action to which the layer'3 has been subjected. On the other hand, the separating layers 4 and 6 have disappeared entirely and the image layers 3, 5 and 6 lie directly adjacent to, and slightly intermeshing with, each other. The cavities 8 are now quasi molten into smooth globular shape and substantially lledlby solid matter originating from the ad- .jacent dissolved separating layers 4 and 6, re'- spectively, and/or from the liquid which has been used for the treatment. Moreover, in the manner which will be hereinafter described, a further layer forming a hard surface coating has been deposited at 9, forming an intimate joint with the uppermost image layer 1. Thus, a substantially homogeneous layer is formed by the layers 2, 3, 5,'1, 9 which have intimately grown together, due to the swelling and dissolving action to which these layers have been subjected.

' Where the image layers consist of gelatine, the liquid which is used in the treatment of the lm comprises substances causing swelling of the gelatine or Asolvents for gelatine suitably diluted to obviate complete solution of the gelatine. liundamentally the desired eect is already produced by the exclusive use of a dilute acid or equivalent means such as potassium hydroxide or sodium hydroxide solution, in that with maximum swelling of the .gelatine imagelayers 3, 5, 1, the rough edges of the tiny hollows in the interior of the layers are transformed to a smooth form. Since however acids or caustic alkalies alo'ne or in combination with water destroy the colours, or at I'[5 tion while the subsequent imbibition proceeds novel process analyzes as follows:

ous or alcohol-aqueous chloral hydrate solution.

While this portion of the mixture serves for swelling Vthe mixture, the mixture may furthermore comprise a chlorinated' aliphatic alcohol of suitable strength in connection with non-chlorinated aliphatic alcohols Aor their derivatives, in order to dissolve the intermediate-o1; blocking layers;

' According to a furtherfeature of the invention Va dissolved colloid which is soluble'to a sumcient extent in the mixture in question, advantageously primary acetyl cellulose, may be applied in thesame operation or in succession. Thus, after the solvents have been evaporated, a multi-colour image layer 3,5, 1, as per Figure '2 is formed which is hard at its surface, but

elastic, perfectly homogeneous, and whereinv the blocking layers 41 and 6 l(Figure l) 'have been dissolvedv and sucked up or absorbed by the adjacent image layers 3, 5,*1.

A preferred mixture whichv may be used in my Parts by volume Aqueous sodium salicylate solution of 10% strength Y 35 Chlorinated ethyl alcohol 30 Amy] alcnhnl Ethyl alcohol 10 Methyl alcohol Y 15 Solactol (lactic-acid ethyl ester) 5 Triacetin (p oly-glycerine derivative) 2 'In this mixture jifpartfby weight of primary acetylcellulose or cellulose triacetate may be dissolved or the lm may be subjected vto an aft- It-will'be understood "that Vthe substances herei'nbefore statedby wayaofexample may be subzstituted by equivalent substances causing` the same' eii'ects and that Vthe percentages may be 'yaried Vaccording "to the properties ofthe lm material tn betreated.- For instance, diacetone same index' Ottenaction as the imagezlayers in @order tol-prevent detrimental optical elects by the cavitie's'in the image layers lled up by these j solid substances.

The treatment of-` the colour nlm may be effe'cted by. applying the mixture to the lm sur- Vface or by passing the ilm through va. bath of the mixture. The former has been found more reliable and advantageous; gAccording to the invention the. improving process can to a certain Vextent be undertaken in steps at intervals, The' image layer of the colour lm is'in this case rst Y 'treated with the mixture according to the invenaaiasa'r gradually in a. time spread over severaldays. Such a method permits accurate dosing of the substancesV to be employed in combination with a suitable colloidal suspension penetrating the surface and hardening it. It is alsopossible to proceedby. puttingth mixture into a solution of '10W viscosity of for instance gelatine'or agar-agarand then in a further stage of the process closing this to the outside with a coating of' a material 'having a higher mechanical resistability'than the image layers, for example cellulose esters, highly polymerisedcolloids, or the like forming a homogeneous combination with the ltop layer of the illm and being impermeable` or repellent to water., such as indicated at 9 in Figure 2.

Where the image layers consist substantially sulphonic acid salts or chloral hyd rate either alone or in suitable mixture.

I contemplate, moreover, to a'dd to the liquid used in my novel process for the treatment of the film, 4substances adapted to change the superficial tension between the lm material and the liquid and to increase the adhesion between the film and the liquid, such as, for example1 a colloid dispersion with'water as a dispersing medium, whereby the liquid used in the treatment will more readily penetrate into the lm and act upon the same in the desired manner;

A colour film treated inaccordancejwith the invention exhibitsimprovement in regard to the clarity of the colour images and increased transparency. Y I claim: f j

1. The 'process of treatinga coloriilmconsisting of a plurality of superimposed 'atine layers containing subtractive dye' i1'nages;.fsaid layers being separated by.Av other gelatine' layers softer than said image layers.- whichfconsists in subjecting' said film tothe actionfof .a neutral agent which has a swelling i elect upon said image layers and a dissolvingelectluponsaid separating layers in such manner andi-for such time as to cause said separating layers. to be absorbed and takenup by the adjacent gelatine image layers, with the result that said layers will .j i inY directly together elimination of said.

Separating layers, said absorption andjdissoluintersticesl left .by the removalvof 'the sensitive silver salts. f Y f 2. The process of treating a c'olor lm con- Aof a plurality of superimposed gelatine layers containing subtractive dyef images, said layers being separated by other gelatine 'layers softer than said image-layers, which consists in Vsubjecting said lm to the' action of' a. neutral agent which has a swelling eii'ect upon saidA image layers and a dissolving effect. upon said separating layers in such manner and-for such time as to cause Said separatinglayers to be absorbed and.

Vtaken up by the adjacent gelatine image layers,

with the .result that said layerswill join directly `togetherwith elimination oi said separating layers, said absorption and dissolution causingsaid separating layers to ll up theintersticesleft by the removal of the sensitive silver salts, said dissolution and swelling resulting `from the' use of a solution containing alkylfatty acid esters'.- r

" FRIEDRICH Joueur; .nicola s'ronr.I

t i on,caav.using said separating layers to" ll unthe 

